An example of a conventional foldable cellular phone terminal is shown in FIGS. 8A and 8B. In FIGS. 8A and 8B, “801” denotes an upper housing, “802” a lower housing “803” a hinge, “804” an upper printed board, “805” a lower printed board, “806” a flexible printed wiring board, “807” an external antenna, “808” a strip line antenna, “809” an upper connector, “810” a lower connector and “811” a feeding point for the strip line antenna 808.
In the upper and lower housings 801 and 802 acting as two split pieces folded on each other by the hinge 803 in the arrangement shown in FIGS. 8A and 8B, a portion of a conductive pattern line on the flexible printed wiring board 806 for electrically connecting the upper printed board 804 and the lower printed board 805 is used as the strip antenna 808 and a portion of the upper connector 809 acts as the feeding point 811 for the strip line antenna 808 as disclosed in Japanese Patent Laid-Open Publication No. 10--3.08618(1998).
Meanwhile, FIGS. 9A and 9B show an example of an arrangement in which an external antenna used for both transmission and reception is provided in a lower housing. In FIGS. 9A and 9B, “901” denotes an upper housing, “902” a lower housing, “903” a hinge, “904” an upper printed board, “905” a lower printed board, “906” a flexible printed wiring board, “907” an external antenna, “908” a built-in antenna, “909” an upper connector and “910” a lower connector. In this case, the built-in antenna 908 is provided in the lower housing 902.
Furthermore, FIGS. 10A and 10B show an example of an arrangement in which one turn of a flexible printed wiring board is passed through a hinge. In FIGS. 10A and 10B, “1001” denotes an upper housing, “1001a” a front casing of the upper housing 1001, “1001b” a rear cover of the upper housing 1001, “1001c” a hinge of the upper housing 1001, “1001d” and “1001e” semicircular hinges of the upper housing 1001, “1002” a lower housing, “1002a” a front casing of the lower housing 1002, “1002b” a rear cover of the lower housing 1002, “1002c” a hinge of the lower housing 1002, “1002d” and “1002e” semicircular hinges of the lower housing 1002, “1003” an external antenna, “1004” a receiver, “1005” a display unit, “1006” dial buttons, “1007” a transmitter, “1008” a flexible printed wiring board and “1009” a coaxial cable. In this case, the upper housing 1001 provided with the external antenna 1003 and the receiver 1004 and the lower housing 1002 provided with the transmitter 1007 are rotated about an axis of the hinges 1001c and 1002c so as to be folded on each other.
The semicircular hinges 1001d and 1001e disposed at a central portion of the hinge 1001c and the semicircular hinges 1002d and 1002e disposed at a central portion of the hinge 1002c are formed hollowly. One turn of the flexible printed wiring board 1008 is passed along an inside diameter of the semicircular hinges 1001d, 1001e, 1002d and 1002e, while the coaxial cable 1009 is inserted into the turn of the flexible printed wiring board 1008 and extends along the flexible printed wiring board 1008 so as to be connected to the external antenna 1003 as disclosed in Japanese Patent Laid-Open Publication No. 6-311216 (1994).
However, in the conventional cellular phone terminal shown in FIGS. 8A and 8B, such a problem arises that since shape of the strip line antenna 808 formed on the flexible printed wiring board 806 changes greatly between a folding state and an unfolding state of the conventional cellular phone terminal, its impedance characteristics change extraordinarily. In addition, in case element duration is equal to about (λ/2), such a drawback is also incurred that since electric current is concentrated at the strip line antenna 808, introduction of noise into other signal conductor lines becomes intense.
Meanwhile, in case the built-in antenna 908 is provided in the lower housing 902 as shown in FIGS. 9A and 9B, the lower housing 902 is usually gripped by a hand when the prior art cellular phone terminal is held by the hand, so that deterioration of characteristics of the built-in antenna 908 becomes heavier disadvantageously.
Moreover, in case a strip line antenna is formed on the flexible printed wiring board 1008 and element duration is not more than (λ/2) in the known arrangement of FIGS. 10A and 10B in which one turn of the flexible printed wiring board 1008 is passed along an inside diameter of the hollow formed at the central portion of the hinges 1001c and 1002c so as to be passed therethrough, electric currents flow in opposite directions on the strip line antenna wound one turn so as to cancel each other, thereby resulting in inconvenient drop of radiant efficiency.